Block copolymer compositions containing substantially inert thermoelastic extenders

ABSTRACT

The present invention is at least a two-component thermoplastic elastomeric composition comprising at least one block copolymer wherein the composition has essentially the same comparative elasticity, high temperature serviceability and hardness as the unmodified, undiluted (neat) block copolymer portion of the composition. The composition also shows enhanced thermal stability and processibility and is well suited for fabricating elastic moldings, films and fibers as well as for formulating with asphalts, adhesives and sealants. The novel thermoplastic elastomeric composition comprises (a) from about 50 to about 99 percent by weight of at least one block copolymer and (b) about 1 to about 50 percent by weight of at least one ethylene interpolymer having a density from about 0.855 g/cc to about 0.905 g/cc, wherein the ethylene interpolymer in the amount employed is a substantially inert extender of the block copolymer and the composition is further characterized as having: 
     i. storage moduli throughout the range of −26° C. to 24° C. of less than about 3.5×10 9  dynes/cm 2 , 
     ii. a ratio of storage modulus at −26° C. to storage modulus at 24° C. of less than about 4, and 
     iii. storage moduli at −26° C. and 24° C. about 0.2 to about 3 times higher than the storage moduli at −26° C. and 24° C., respectively, of the neat block copolymer portion of the composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/663,870filed Jun. 19, 1996, now abandoned, which is a continuation ofapplication Ser. No. 08/298,238, filed Aug. 29, 1994, now abandoned,which is a continuation-in-part of patent application Ser. No.08/252,489, filed Jun. 1, 1994, and is related to patent applicationSer. No. 07/776,130, filed Oct. 15, 1991, now U.S. Pat. No. 5,272,236;patent application Ser. No. 07/939,281, filed Sep. 2, 1992, now U.S.Pat. No. 5,278,272; patent application Ser. No. 07/945,034, filed Sep.15, 1992; and patent application Ser. No. 08/045,330, filed Apr. 8,1993.

FIELD OF THE INVENTION

This invention relates to thermoplastic elastomeric compositionscontaining substantially inert thermoelastic extenders. In particular,the invention relates to thermoplastic elastomeric compositionscomprising block copolymers in blend combination with substantiallyinert ethylene interpolymers.

BACKGROUND OF THE INVENTION

Various thermoplastic elastomeric compositions are well-known andinclude thermoplastic urethanes, thermoplastic polyesters, amorphouspolypropylenes, chlorinated polyethylenes, ethylene/propylene rubbers,crosslinked and uncrosslinked EPDM (ethylene-propylene-nonconjugateddiene monomer) systems, and styrene block copolymers. Styrene blockcopolymers, which are sold under the brand names of Vector, Kraton andSolprene as supplied respectively by Dexco Polymers, Shell Oil Companyand Phillips Petroleum, are considered to be very versatilethermoplastic elastomers.

Styrene block copolymers are also recognized as strong, flexible highperformance elastomers that do not require vulcanization and yet exhibitexcellent elasticity over a wide range of service temperatures. Due totheir unique molecular structure and versatility, styrene blockcopolymers are used in a wide spectrum of enduses such as moldablegoods, automotive interior and exterior parts, medical devices, and thelike.

Styrene block copolymers are available with linear, diblock, triblockand radial molecular structures. Each polymer molecule consists of astyrenic block segment and a rubber monomer block segment. The rubbersegment may consist of saturated or unsaturated monomer units such asethylene/butene and ethylene/propylene, or butadiene and isoprene,respectively. Styrene block copolymers having saturated rubber monomersegments typically exhibit improved thermal, oxidative and processingstability, better weather resistance, and higher temperatureserviceability when compared to copolymers consisting of unsaturatedrubber monomer segments.

Although styrene block copolymers are very useful, they have a number ofdeficiencies. These materials are relatively expensive and due to theirfairly difficult manufacturing requirements are often in short supply.Moreover, due to the inability of their particles or pellets toexpediently melt and fuse together with the application of heat, styreneblock copolymers with saturated rubber monomer segments are fairlydifficult to formulate and process. Processing in conventional equipmentsuch as, for example, a Banbury mixer, is typically characterized by aninitial induction or delay period which adds to processing costs. Asanother disadvantage, this delay, which in effect constitutes anadditional heat history, can contribute to the overall thermal andprocessing instability of the copolymer.

Because of high material costs, shortages and processing difficulties,it is desirable to provide blend components that can extend availablequantities of styrene block copolymers without substantially alteringthe key elastic properties of the latter. It is also desirable toprovide component materials that function as processing aids or fusionpromoters whereby the delay times associated with thermally processingstyrene block copolymers having saturated rubber monomer segments can besubstantially reduced. Further, it is desirable to improve theproperties of block copolymers having unsaturated rubber monomer blocksegments without the higher manufacturing costs typically associatedwith block copolymers having saturated rubber monomer segments.

There has been a long felt need to mitigate the above difficultiesassociated with conventional thermoplastic elastomeric materials but,unfortunately, prior art efforts to do so have not been entirelysuccessful. Prior art proposals to facilitate the use of ordinarythermoelastic materials tend to involve curing steps or multicomponentcompositions with extensive formulating requirements. For example, ShellOil Company in its Kraton brochure indicates the Kraton materials arehighly extendable presumably by specific combinations of involvingfillers, resins and oils. On page 3 of the brochure, Kraton D compoundsand Kraton G compounds are said to contain other suitable ingredients.Further, where other ingredients are used, including fillers and oils incombination or alone, it is expected that special handling and equipmentwould be required for uniform admixing with solid block copolymerresins.

Where ordinary thermoelastic materials, such as, for example,ethylene/vinyl acetate (EVA) copolymers, are used as single-componentextenders for block copolymers, the elastic, rheological, stability orhardness properties of the final composition tend to vary substantiallyrelative to neat compositions of the respective block copolymer. Stillother prior art disclosures involving ethylene/α-olefin interpolymers incombination with block copolymers such as, for example, U.S. Pat. No.5,272,236, which discloses blends of substantially linear ethyleneinterpolymers and styrene butadiene copolymers, and Plastics Technology,August 1994, page 54, which mentions similar blends useful for moldedgoods, do not teach or render obvious the specific requirements thatenable the use of such materials as substantially inert extenders, nordisclose the surprising benefits that can be realized by doing so.

SUMMARY OF THE INVENTION

It has been discovered that the combination of at least one blockcopolymer and with specified amounts of at least one particular ethyleneinterpolymer yields a thermoplastic elastomeric composition havingessentially the same elastic and hardness properties as the blockcopolymer portion of the composition. The particular effect of theethylene interpolymer can be described as a substantially inertthermoelastic extender of the styrene block copolymer.

Thus one aspect of the present invention is a thermoplastic elastomericcomposition comprising (a) from about 50 to about 99 percent by weightof the total composition of at least one block copolymer and (b) fromabout 1 to about 50 percent by weight of the total composition of atleast one thermoelastic ethylene interpolymer having a density fromabout 0.855 g/cc to about 0.905 g/cc, wherein the thermoelastic ethyleneinterpolymer in the amount employed is a substantially inertthermoelastic extender of the block copolymer and the composition isfurther characterized as having:

i. storage moduli throughout the range of −26° C. to 24° C. of less thanabout 3.5×10⁹ dynes/cm²,

ii. a ratio of storage modulus at −26° C. to storage modulus at 24° C.of less than about 4, and

iii. storage moduli at −26° C. and 24° C. about 0.2 to about 3 timeshigher than the storage moduli at −26° C. and 24° C., respectively, ofthe neat block copolymer portion of the composition.

Another aspect of the present invention is a method of making afabricated article in the form of a film, fiber and molding from thenovel thermoplastic elastomeric composition.

In still another aspect, the present invention provides a fabricatedarticle in the form of a film, fiber or molding made from the novelthermoplastic elastomeric composition.

In addition to utility as a substantially unaltered neat blockcopolymer, the novel composition also exhibits the benefit of improvedprocessability. Particular ethylene interpolymers, functioning as fusionpromoters and processing aids, substantially reduce the processing delaytimes characteristic of styrene block copolymers having saturated rubbermonomer units.

As still another benefit of the present invention, the novel compositionalso exhibits improved stability when exposed to stresses such as heat,shear and ultraviolet radiation relative to a comparative styrene blockcopolymer having unsaturated rubber monomer units.

The functioning of select ethylene interpolymers as substantially inertthermoelastic extenders is surprising since, although such thermoelasticpolymers are generally elastic, their properties can differsubstantially from those of block copolymers.

While the invention is not limited to any particular theory ofoperation, the surprising enhancements are believed to be due to theunique compatibility obtainable with elastic and, preferably,compositionally uniform ethylene interpolymers, particularlyhomogeneously branched ethylene interpolymers. Such utility andimprovements are not obtainable with ordinary thermoelastic materialssuch as, for example, ethylene/vinyl acetate (EVA) copolymers even athigh vinyl acetate levels, nor with ethylene interpolymers havingpolymer densities substantially greater than about 0.905 g/cc.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plot of the dynamic storage modulus versus temperature forExamples 1-5 as determined using a Rheometrics Solid Analyzer RSA-II.

FIG. 2 is a plot of the dynamic storage modulus versus temperature forExamples 1-5 as predicted based on weight average contributions of thecomponent materials.

FIG. 3 is a plot of the dynamic complex viscosity versus shear rate forExamples 1-5 as determined using a Rheometrics Rheometer RMS-800 at 190°C.

FIG. 4 is a plot of the dynamic storage modulus versus temperature forExamples 6-10 as determined using a Rheometrics Solid Analyzer RSA-II.

FIG. 5 is a plot of the dynamic storage modulus versus temperature forExamples 6-10 as predicted based on weight average contributions of thecomponent materials.

FIG. 6 is a plot of the dynamic complex viscosity versus shear rate forExamples 6-10 as determined using a Rheometrics Rheometer RMS-800 at190° C.

FIG. 7 is a plot of the dynamic storage modulus versus temperature forExamples 11-15 as determined using a Rheometrics Solid Analyzer RSA-II.

FIG. 8 is a plot of the dynamic complex viscosity versus shear rate forExamples 11-15 as determined using a Rheometrics Rheometer RMS-800 at190° C.

FIG. 9 is a plot of the dynamic storage modulus versus temperature forExamples 6, 7, 17-20 as determined using a Rheometrics Solid AnalyzerRSA-II.

FIG. 10 is a plot of the Haake torque response versus time for Example12 at 240° C. as determined using Haake torque mixer.

FIG. 11 is a plot of the Haake torque response versus time for Example11 at 240° C. as determined using Haake torque mixer.

FIG. 12 is a plot of the Haake torque response versus time for Example22 at 240° C. as determined using Haake torque mixer.

FIG. 13 is a plot of the dynamic storage modulus versus temperature forExamples 7, 23-26 as determined using a Rheometrics Solid AnalyzerRSA-II.

DETAILED DESCRIPTION OF THE INVENTION

The referred block copolymer has block segments of styrenic units andblock segments of rubber monomer units such as butadiene, isoprene,ethylene/propylene and ethylene/butene. The preferred substantiallyinert thermoelastic ethylene interpolymer is a homogeneously branchedethylene interpolymer, and more preferably a substantially linearethylene polymer characterized as having:

(a) a melt flow ratio, I₁₀/I₂, ≧5.63,

(b) a molecular weight distribution, M_(w)/M_(n), defined by theequation: M_(w)/M_(n)≦(I₁₀/I₂)−4.63, and

(c) a critical shear rate at the onset of surface melt fracture of atleast 50 percent greater than the critical shear rate at the onset ofsurface melt fracture of a comparative linear ethylene polymer havingabout the same I₂ and M_(w)/M_(n).

The term “interpolymer” is used herein to indicate a copolymer, or aterpolymer, or the like, where, at least one other comonomer ispolymerized with ethylene to make the interpolymer.

The term “thermoplastic” is used herein to indicate polymers or polymercompositions that are substantially thermally extrudable or deformablealbeit relatively aggressive conditions may be required.

The term “thermoelastic” is used herein to mean a thermoplastic resinhaving elastic properties, wherein elastic properties means the resinhas a thin film (i.e., <4 mils) one percent secant modulus of less thanabout 15,000 psi, or an elongation at break of greater than about 450%,or the following dynamic mechanical storage modulus (E′) properties:

(a) storage moduli in the range of about −26° C. to about 24° C. of lessthan about 5×10⁹ dynes/cm², and

(b) a ratio of storage modulus at −26° C. to storage modulus at 24° C.of less than about 8.

The term “elastomeric” or “elastomer” is used herein to mean a materialor composition having dynamic mechanical storage moduli (E′) in therange of about −26° C. to about 24° C. of less than about 3.5×10⁹dynes/cm², and a ratio of storage modulus at −26° C. to storage modulusat 24° C. of less than about 4, wherein a “perfectly elastic” materialwould have a ratio of 1.

The term “substantially inert thermoelastic extender” is used herein tomean a thermoelastic polymer that at specified addition amounts does notsubstantially alter either the elasticity, rheology, high temperatureserviceability or hardness that is characteristic of the neat blockcopolymer that is admixed with the thermoelastic polymer to prepare thenovel composition of the present invention. The effect of the selectthermoelastic polymer is such that the novel composition ischaracterized as having (1) storage moduli at −26° C. and 24° C. no lessthan about 0.2 times lower and no more than about 3 times higher thanthe storage moduli at −26° C. and 24° C. of the respective neat blockcopolymer (i.e., storage moduli of the composition at −26° C. and 24° C.is about 0.2 to about 3 times higher than the storage moduli at −26° C.and 24° C., respectively, of the neat block copolymer portion of thecomposition), (2) a dynamic complex viscosity the throughout the shearrate range of 10 to 100 l/sec of about 0 to about 50 percent lower thanthe respective neat block copolymer, and (3) less than or equal to about±3 units difference in Shore A hardness (as measured by ASTM-D2240 whencompared to the respective neat block copolymer.

Suitable substantially inert thermoelastic extenders for use inpreparing the thermoplastic elastomeric compositions of the presentinvention are ethylene interpolymers, preferably homogeneously branchedethylene interpolymers, and more preferably substantially linearethylene interpolymers. Preferred ethylene interpolymers also containingat least one C₃-C₂₀ α-olefin.

The terms “ultra low density polyethylene” (ULDPE), “very low densitypolyethylene” (VLDPE) and “linear very low density polyethylene”(LVLDPE) have been used interchangeably in the polyethylene art todesignate the polymer subset of linear low density polyethylenes havinga density less than or equal to about 0.915 g/cc. The term “linear lowdensity polyethylene” (LLDPE) is then applied to those linearpolyethylenes having a density above about 0.915 g/cc. Onlyethylene/α-olefin interpolymers having a polymer density less than about0.905 g/cc are a part of the present invention. As such, the familyknown as LLDPE is not considered a part of to the present inventionalthough such may be employed to affect other enhancements.

The terms “heterogeneous” and “heterogeneously branched” are used hereinin the conventional sense in reference to a linear ethylene interpolymerhaving a comparatively low short chain branching distribution index. Theshort chain branching distribution index (SCBDI) is defined as theweight percent of the polymer molecules having a comonomer contentwithin 50 percent of the median total molar comonomer content. The shortchain branching distribution index of polyolefins that arecrystallizable from solutions can be determined by well-knowntemperature rising elution fractionation techniques, such as thosedescribed by Wild et al., Journal of Polymer Science, Poly. Phys. Ed.,Vol. 20, p. 441 (1982), L. D. Cady, “The Role of Comonomer Type andDistribution in LLDPE Product Performance,” SPE Regional TechnicalConference, Quaker Square Hilton, Akron, Ohio, October 1-2, pp. 107-119(1985), or U.S. Pat. No. 4,798,081, the disclosures of all which areincorporated herein by reference. Heterogeneously branched linearethylene interpolymers and particularly, heterogeneously branched linearethylene/α-olefin interpolymers typically have a SCBDI less than about30 percent.

The preparation of heterogeneously branched linear ethyleneinterpolymers is not a critical aspect the present invention.Heterogeneously branched linear ethylene interpolymers useful in thepresent invention, such as the class known interchangeably as ULDPE andVLDPE, may be prepared by any of the well-known methods such the methodsdescribed by Anderson et al. in U.S. Pat. No. 4,076,698, the disclosureof which is incorporated by reference, or described in Kirk-OthmerEncyclopedia of Science and Technology, Volume 14, pages 242-282 (2n ed.1967).

Suitable unsaturated comonomers useful for polymerizing with ethylene toprepare suitable heterogeneously branched linear ethylene interpolymersinclude, for example, ethylenically unsaturated monomers, conjugated ornon-conjugated dienes, polyenes, etc. Examples of such comonomersinclude C₃-C₂₀ α-olefins as propylene, isobutylene, 1-butene, 1-hexene,4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, and thelike. Preferred comonomers include propylene, 1-butene, 1-hexene,4-methyl-1-pentene and 1-octene, and 1-octene is especially preferred.

Other suitable monomers include styrene, halo- or alkyl-substitutedstyrenes, tetrafluoroethylene, vinylbenzocyclobutane, 1,4-hexadiene,1,7-octadiene, and cycloalkenes, e.g., cyclopentene, cyclohexene andcyclooctene. The interpolymer can be amorphous or semi-crystalline witha random, atactic, isotactic or syndiotactic molecular structure, butpreferably the interpolymer is a random semi-crystalline polymer.Preferred heterogeneously branched linear ethylene interpolymers areethylene interpolymerized with at least one C₃-C₂₀ α-olefin and mostpreferably, ethylene/1-octene copolymers.

Commercial examples of heterogeneously branched linear interpolymerssuitable for use in the present invention include ATTANE ULDPE polymerssupplied by the Dow Chemical Company and FLEXOMER VLDPE polymerssupplied by Union Carbide Corporation.

The term “homogeneously branched” is defined herein to mean that (1) theα-olefin comonomer(s) is (are) randomly distributed within a givenmolecule, (2) substantially all of the copolymer molecules have the sameethylene-to-comonomer ratio, (3) the interpolymer is characterized by anarrow short chain branching distribution where the short chainbranching distribution index is greater than 30 percent, more preferablygreater than 50 percent, and (4) the interpolymer essentially lacks ameasurable high density (crystalline) polymer fraction as measured byknown fractionation techniques such as, for example, a method thatinvolves polymer fractional elutions as a function of temperature.

The homogeneously branched ethylene interpolymers for useful admixingwith block copolymers can be linear ethylene interpolymers, orpreferably, substantially linear ethylene interpolymers. Both thesubstantially linear and the homogeneously branched linear ethyleneinterpolymers are ethylene interpolymers having a short chain branchingdistribution index (SCBDI) greater than about 30 percent. Thesubstantially linear interpolymers have a single melting points asopposed to traditional Ziegler polymerized polymers having two or moremelting points as determined using differential scanning calorimetry(DSC).

The homogeneously branched linear ethylene interpolymers useful foradmixing with block copolymers to prepare the thermoplastic elastomericcomposition of the present invention are ethylene polymers which do nothave long chain branching, but do have short chain branches derived fromthe comonomer polymerized into the interpolymer which are homogeneouslydistributed both within the same polymer chain and between differentpolymer chains. That is, homogeneously branched linear ethyleneinterpolymers have an absence of long chain branching just as is thecase for the linear low density polyethylene polymers or linear highdensity polyethylene polymers made using uniform branching distributionpolymerization processes as described, for example, by Elston in U.S.Pat. No. 3,645,992, the disclosure of which is incorporated herein byreference.

The homogeneously branched linear ethylene interpolymers are not highpressure, free-radical initiated polyethylene which is well-known tothose skilled in the art to have numerous long chain branches, nor arethey traditional heterogeneously branched linear low densitypolyethylene. Suitable unsaturated comonomers useful for polymerizingwith ethylene to prepare suitable homogeneously branched linear ethyleneinterpolymers include, for example, ethylenically unsaturated monomers,conjugated or non-conjugated dienes, polyenes, etc. Examples of suchcomonomers include C₃-C₂₀ α-olefins as propylene, isobutylene, 1-butene,1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene,and the like. Preferred comonomers include propylene, 1-butene,1-hexene, 4-methyl-1-pentene and 1-octene, and 1-octene is especiallypreferred. Other suitable monomers include styrene, halo- oralkyl-substituted styrenes, tetrafluoroethylenes,vinylbenzocyclobutanes, butadienes, isoprenes, pentadienes, hexadienes,octadienes, and cycloalkenes, e.g., cyclopentene, cyclohexene andcyclooctene. Typically, the homogeneously branched linear ethyleneinterpolymer is a copolymer, wherein ethylene is copolymerized with oneC₃-C₂₀ α-olefin. Most preferably, the homogeneously branched linearethylene interpolymer is a copolymer of ethylene and 1-octene.

The preparation of homogeneously branched linear ethylene/(x-olefininterpolymers is not a critical aspect of the present invention.Homogeneously branched linear ethylene/α-olefin interpolymers can beprepared in conventional polymerization processes using Ziegler-typecatalysts such as, for example, zirconium and vanadium catalyst systemsas well as using metallocene catalyst systems such as, for example,those based on hafnium. Ewen et al. disclosure in U.S. Pat. No.4,937,299 and Tsutsui et al. disclosure in U.S. Pat. No. 5,218,071, bothof which are incorporated herein by reference are, are illustrative.

Commercial examples of homogeneously branched linear interpolymerssuitable for use in the present invention include TAFMER polymerssupplied by the Mitsui Chemical Company and EXACT polymers supplied byExxon Chemical Company.

The substantially linear ethylene interpolymers used in the presentinvention are a unique class of compounds that are further defined inapplication Ser. No. 07/776,130 filed Oct. 15, 1991, now U.S. Pat. No.5,272,236, and in application Ser. No. 07/939,281 filed Sep. 2, 1992,now U.S. Pat. No. 5,278,272, both of which are incorporated herein byreference in their entirety.

Substantially linear ethylene interpolymers are a completely differentclass of homogeneously branched ethylene polymers. They differsubstantially from the well-known class of conventional homogeneouslybranched linear ethylene interpolymers described by Elston in U.S. Pat.No. 3,645,992, and moreover, they are not in the same class asconventional heterogeneous Ziegler polymerized linear ethylene polymers(e.g., ultra low density polyethylene, linear low density polyethyleneor high density polyethylene made, for example, using the techniquedisclosed by Anderson et al. in U.S. Pat. No. 4,076,698), nor are theyin the same class as high pressure, free-radical initiated highlybranched high pressure polyethylenes such as, for example, low densitypolyethylene (LDPE), ethylene-acrylic acid (EAA) copolymers andethylene-vinyl acetate (EVA) copolymers.

The substantially linear ethylene interpolymers useful in this inventionhave excellent processability, even though they have relatively narrowmolecular weight distribution. Surprisingly, the melt flow ratio(I₁₀/I₂) of the substantially linear ethylene interpolymers can bevaried widely and essentially independently of the polydispersity index(i.e., the molecular weight distribution, M_(w)/M_(n)). This surprisingbehavior is completely contra to homogeneously branched linear ethyleneinterpolymers such as those described, for example, by Elston in U.S.Pat. No. 3,645,992 and heterogeneously branched conventional Zieglerpolymerized linear polyethylene interpolymers such as those described,for example, by Anderson et al. in U.S. Pat. No. 4,076,698. Both linearethylene interpolymer types have rheological properties such that as thepolydispersity index increases, the I₁₀/I₂ value also increases.

The term “substantially linear” means that the polymer backbone issubstituted with about 0.01 long chain branch/1000 carbons to about 3long chain branches/1000 carbons, more preferably from about 0.01 longchain branches/1000 carbons to about 1 long chain branch/1000 carbons,and especially from about 0.05 long chain branch/1000 carbons to about 1long chain branch/1000 carbons.

The term “long chain branching” is defined herein as a chain length ofat least about 6 carbons, above which the length cannot be distinguishedusing ¹³C nuclear magnetic resonance spectroscopy, yet the long chainbranch can be about the same length as the length of the polymerbackbone.

Long chain branching is determined by using ¹³C nuclear magneticresonance (NMR) spectroscopy and is quantified using the methoddescribed by Randall (Rev. Macromol. Chem. Phys., Chpt. 29, Vols. 2&3,p. 285-297), the disclosure of which is incorporated herein byreference.

Suitable unsaturated comonomers useful for polymerizing with ethylene toprepare suitable substantially linear ethylene interpolymers include,for example, ethylenically unsaturated monomers, conjugated ornon-conjugated dienes, polyenes, etc. Examples of such comonomersinclude C₃-C₂₀ α-olefins as propylene, isobutylene, 1-butene, 1-hexene,4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, and thelike. Preferred comonomers include propylene, 1-butene, 1-hexene,4-methyl-1-pentene and 1-octene, and 1-octene is especially preferred.Other suitable monomers include styrene, halo- or alkyl-substitutedstyrenes, tetrafluoroethylene, vinylbenzocyclobutane, 1,4-hexadiene,1,7-octadiene, and cycloalkenes, e.g., cyclopentene, cyclohexene andcyclooctene. Preferred substantially linear ethylene interpolymers foruse in the present invention are interpolymers of ethylene with at leastone C₃-C₂₀ α-olefin and/or C₄-C₁₈ diolefin. Copolymers of ethylene and aC₃-C₂₀ α-olefin of are especially preferred.

The density of the ethylene interpolymers for use in the presentinvention, as measured in accordance with ASTM D-792, is generally inthe range from about 0.855 grams/cubic centimeter (g/cc) to about 0.905g/cc, preferably about 0.86 g/cc to about 0.89 g/cc, more preferablyabout 0.865 g/cc to about 0.885 g/cc. The density limitation is criticalfor obtaining the required compatibility and inertness of the ethyleneinterpolymer. At densities above 0.905 g/cc, ethylene interpolymers aregenerally non-elastomeric. At densities below 0.855 g/cc, theinterpolymer is fairly tacky and difficult to process and handle.

The molecular weight of the ethylene interpolymers is convenientlyindicated using a melt index measurement according to ASTM D-1238,Condition 190° C./2.16 kilogram (kg), formerly known as “Condition E”and also known as I₂. Melt index is inversely proportional to themolecular weight of the polymer. Thus, the higher the molecular weight,the lower the melt index, although the relationship is not linear. Themelt index for the ethylene interpolymers useful herein is generallyfrom about 0.01 gram/10 minutes (g/10 min.) to about 100 g/10 min.,preferably from about 0.1 g/10 min. to about 40 g/10 min., andespecially from about 1 g/10 min. to about 10 g/10 min.

Other measurements useful in characterizing the molecular weight ofethylene interpolymers involve melt index determinations with higherweights, such as, for common example, ASTM D-1238, Condition 190° C./10kg (formerly known as “Condition N” and also known as I₁₀). “Melt flowratio” is defined herein as the ratio of a higher weight melt indexdetermination to a lower weight determination, and for measured I₁₀ andthe I₂ melt index values, the melt flow ratio is conveniently designatedas I₁₀/I₂. The I₁₀/I₂ of both heterogeneous and homogeneously branchedlinear ethylene interpolymers is generally greater than about7.

Unlike the linear ethylene interpolymers of the present invention whichpossess no substantial long chain branching, for the substantiallylinear ethylene interpolymers used herein, the melt flow ratio actuallyindicates the degree of long chain branching, i.e., the higher theI₁₀/I₂ melt flow ratio, the more long chain branching in the polymer.The I₁₀/I₂ ratio of the substantially linear ethylene interpolymers ispreferably at least about 5.63, and especially from about 5.63 to about20, and most especially from about 6 to about 15.

The “rheological processing index” (PI) which is defined herein as theapparent viscosity in kpoise of a polymer measured by a gas extrusionrheometer (GER), can also be used to distinguish substantially linearethylene interpolymers. The gas extrusion rheometer is described by M.Shida, R. N. Shroff and L. V. Cancio in Polymer Engineering Science,Vol. 17, No. 11, p. 770 (1977), and in “Rheometers for Molten Plastics”by John Dealy, published by Van Nostrand Reinhold Co. (1982) on pp.97-99, both publications of which are incorporated by reference hereinin their entirety. GER experiments are performed at a temperature of190° C., at nitrogen pressures between 250 to 5500 psig (17-379 bars)using about a 0.754 mm diameter, 20:1 L/D die with an entrance angle of180°. For the substantially linear ethylene polymers used herein, the PIis the apparent viscosity (in kpoise) of a material measured by GER atan apparent shear stress of 2.15×10⁶ dyne/cm². The unique substantiallylinear ethylene interpolymers described herein preferably have a PI inthe range of about 0.01 kpoise to about 50 kpoise, preferably about 15kpoise or less. The substantially linear ethylene interpolymers usedherein have a PI less than or equal to about 70% of the PI of acomparative linear ethylene interpolymer (for example, a homogeneouslybranched linear interpolymer as described by Elston in U.S. Pat. No.3,645,992, or supplied by Exxon Chemical Company as EXACT, or suppliedby Mitsui Chemical Company as TAFMER) having about the same I₂ andM_(w)/M_(n).

To more fully characterize the unique rheological behavior ofsubstantially linear ethylene interpolymers, S. Lai and G. W. Knightrecently introduced (ANTEC '93 Proceedings, INSITE™ TechnologyPolyolefins (ITP)—New Rules in the Structure/Rheology Relationship ofEthylene α-Olefin Copolymers, New Orleans, La., May 1993) anotherrheological measurement, the Dow Rheology Index (DRI), which expresses apolymer's “normalized relaxation time as the result of long chainbranching.” DRI ranges from 0 for polymers which do not have anymeasurable long chain branching (e.g., TAFMER and EXACT products) toabout 15 and is independent of melt index. In general, for low to mediumpressure ethylene polymers (particularly at lower densities) DRIprovides improved correlations to melt elasticity and high shearflowability relative to correlations of the same attempted with meltflow ratios, and for the substantially linear ethylene interpolymers ofthis invention, DRI is preferably at least about 0.1, and especially atleast about 0.5, and most especially at least 0.8. DRI can be calculatedfrom the equation:

DRI=(3652879*τ_(o) ^(1.00649)/η_(o)−1)/10

where τ_(o) is the characteristic relaxation time of the material andη_(o) is the zero shear viscosity of the material. Both τ_(o) and η_(o)are the “best fit” values to the Cross equation, i.e.

η/η_(o)=1/(1+(γ*τ_(o))^(1−n))

where n is the power law index of the material, and η and γ are themeasured viscosity and shear rate, respectively. Baseline determinationof viscosity and shear rate data are obtained using a RheometricsMechanical Spectrometer (RMS-800) under dynamic sweep mode from 0.1 to100 radians/second at 160° C. and a Gas Extrusion Rheometer (GER) atextrusion pressures from 1,000 psi to 5,000 psi (corresponding shearstress from 0.086 to 0.43 MPa) using a 0.754 millimeter diameter, 20:1L/D die at 190° C. Specific material determinations can be performedfrom 140 to 190° C. as required to accommodate melt index variations.

In addition to the onset of draw resonance and various rheologicalcharacterizations, ethylene polymers can also be distinguished by meltflow consequences that are manifested as solid state surface defects.Unlike draw resonance which is observed during drawing and pertains toirregularities in the extrudate dimension, an apparent shear stressversus apparent shear rate plot is used to identify the “melt fracture”phenomena which pertains to surface irregularities. According toRamamurthy in the Journal of Rheology, 30(2), 337-357, 1986, above acertain critical shear rate (in contrast to a critical draw rate for thedraw resonance phenomena), the observed extrudate irregularities may bebroadly classified into two main types: surface melt fracture and grossmelt fracture.

Surface melt fracture occurs under apparently steady flow conditions andranges in detail from loss of specular film gloss to the more severeform of “sharkskin.” In this disclosure, the onset of surface meltfracture (OSMF) is characterized at the beginning of losing extrudategloss at which the surface roughness of the extrudate can only bedetected by 40×magnification. The critical shear rate at the onset ofsurface melt fracture for the substantially linear ethyleneinterpolymers is at least 50 percent greater than the critical shearrate at the onset of surface melt fracture of a comparative linearethylene interpolymer (for example, a homogeneously branched linearinterpolymer as described by Elston in U.S. Pat. No. 3,645,992) havingabout the same I₂ and M_(w)/M_(n).

Gross melt fracture occurs at unsteady extrusion flow conditions, andranges in detail from regular (alternating rough and smooth, helical,etc.) to random distortions. For commercial acceptability, (e.g., foruse as films, coatings and moldings), surface defects should be minimal,if not absent, for good film/molding quality and overall properties. Thecritical shear stress at the onset of gross melt fracture for thesubstantially linear ethylene interpolymers used in the presentinvention is greater than about 4×10⁶ dynes/cm². The critical shear rateat the onset of surface melt fracture (OSMF) and the onset of gross meltfracture (OGMF) will be used herein based on the changes of surfaceroughness and configurations of the extrudates extruded by a GER.

The distribution of comonomer branches for ethylene interpolymers ischaracterized by its SCBDI (Short Chain Branch Distribution Index) orCDBI (Composition Distribution Branch Index) and is defined as theweight percent of the polymer molecules having a comonomer contentwithin 50 percent of the median total molar comonomer content. The CDBIof a polymer is readily calculated from data obtained from techniquesknown in the art, such as, for example, temperature rising elutionfractionation (abbreviated herein as “TREF”) as described, for example,by Wild et al., Journal of Polymer Science, Poly. Phys. Ed., Vol. 20, p.441 (1982), or in U.S. Pat. No. 4,798,081, both disclosures of which areincorporated herein by reference. The SCBDI or CDBI for thesubstantially linear ethylene interpolymer and the homogeneouslybranched linear ethylene interpolymer used in the present invention ispreferably greater than about 30 percent and especially greater thanabout 50 percent.

The substantially linear ethylene interpolymer and the homogeneouslybranched linear ethylene interpolymer used in this invention essentiallylack a measurable “high density” fraction as measured by the TREFtechnique. These homogeneously branched ethylene interpolymers do notcontain a polymer fraction with a degree of branching less than or equalto 2 methyls/1000 carbons.

The “high density polymer fraction” can also be described as a polymerfraction with a degree of branching less than about 2 methyls/1000carbons. Among other benefits, the lack of high density polymer fractionpermits enhanced elasticity for the interpolymers themselves andimproved compatibility when admixed with the block copolymer of thepresent invention.

The substantially linear ethylene interpolymers are also characterizedby a single DSC melting peak. However, for substantially linear ethyleneinterpolymers having a density in the range of about 0.875 g/cc to about0.905 g/cc, the single melting peak may show, depending on DSC equipmentsensitivity, a “shoulder” or a “hump” on it's low melting side thatconstitutes less than 12 percent, typically, less than 9 percent, andmore typically less than of 6 percent of the total heat of fusion of thepolymer. This artifact is believed to be due to intra-polymer chainvariations and is discerned on the basis of the slope of the singlemelting peak varying monotonically through the melting region of theartifact. Such artifacts occur within 34° C., typically within 27° C.,and more typically within 20° C. of the melting point of the singlemelting peak. The single melting peak is determined using a differentialscanning calorimeter standardized with indium and deionized water. Themethod involves about 5-7 mg sample sizes, a “first heat” to about 180°C. which is held for 4 minutes, a cool down at 10°/min. to −30° C. whichis held for 3 minutes, and heat up at 10° C./min. to 140° C. for the“second heat”. The single melting peak is taken from the “second heat”heat flow vs. temperature curve. Total heat of fusion of the polymer iscalculated from the area under the curve. The heat of fusionattributable to this artifact, if present, can be determined using ananalytical balance and weight-percent calculations.

The molecular weight distribution of the ethylene interpolymers used inthe present invention are determined by gel permeation chromatography(GPC) on a Waters 150 high temperature chromatographic unit equippedwith a differential refractometer and three columns of mixed porosity.The columns are supplied by Polymer Laboratories and are commonly packedwith pore sizes of 10³, 10⁴, 10⁵ and 10⁶ Å. The solvent is1,2,4-trichlorobenzene, from which 0.3 percent by weight solutions ofthe interpolymer samples are prepared for injection. The flow rate is1.0 milliliter/minute and the operating temperature is 140° C. with a100-microliter injection size.

The molecular weight determination with respect to the polymer backboneis deduced by using narrow molecular weight distribution polystyrenestandards (from Polymer Laboratories) in conjunction with their elutionvolumes. The equivalent polyethylene molecular weights are determined byusing appropriate Mark-Houwink coefficients for polyethylene andpolystyrene (as described by Williams and Ward in Journal of PolymerScience, Polymer Letters, Vol. 6, p. 621, 1968, incorporated herein byreference) to derive the following equation:

M_(polyethylene) =a*(M_(polystyrene))^(b).

In this equation, a=0.4316 and b =1.0. Weight average molecular weight,M_(w), is calculated in the usual manner according to the followingformula: M_(w)=R w_(i)*M_(i), where w_(i) and M_(i) are the weightfraction and molecular weight, respectively, of the ith fraction elutingfrom the GPC column.

For the substantially inert ethylene interpolymers used in the presentinvention, the M_(w)/M_(n) is generally from about 1.5 to about 8, andespecially from about 1.7 to about 6.5. For the homogeneously branchedlinear ethylene interpolymer and substantially linear ethyleneinterpolymer, the M_(w)/M_(n) is preferably from about 1.5 to about 2.5.

Single site polymerization catalysts, (e.g., the monocyclo-pentadienyltransition metal olefin polymerization catalysts described by Canich inU.S. Pat. No. 5,026,798 or by Canich in U.S. Pat. No. 5,055,438, ordescribed by Stevens et al. in U.S. Pat. No. 5,064,802, the disclosureof all of which are incorporated herein by reference) can be used topolymerize the substantially linear ethylene interpolymers, so long asthe catalysts are used consistent with the methods described in U.S.Pat. No. 5,2727,236 and in U.S. Pat. No. 5,278,272. Such polymerizationmethods are also described in PCT/US 92/08812 (filed Oct. 15, 1992), thedisclosure of which is incorporated herein by reference. However,substantially linear ethylene interpolymers are preferably made by usingsuitable constrained geometry catalysts, especially constrained geometrycatalysts as disclosed in U.S. application Ser. Nos.: 545,403, filedJul. 3, 1990; 758,654, filed Sep. 12, 1991, now issued U.S. Pat. Nos.5,132,380; and 758,660, filed Sep. 12, 1991, the teachings of all ofwhich are incorporated herein by reference.

Suitable cocatalysts for use herein include but are not limited to, forexample, polymeric or oligomeric aluminoxanes, especially methylaluminoxane or modified methyl aluminoxane (made, e.g., as described inU.S. Pat. No. 5,041,584, U.S. Pat. No. 4,544,762, U.S. Pat. No.5,015,749, and/or U.S. Pat. No. 5,041,585, the disclosures of each ofwhich are incorporated herein by reference) as well as inert,compatible, non-coordinating, ion forming compounds. Preferredcocatalysts are inert, non-coordinating, boron compounds.

The polymerization conditions for manufacturing substantially linearethylene interpolymers used herein are preferably those useful in thesolution polymerization process, although the application of the presentinvention is not limited thereto. Slurry and gas phase polymerizationprocesses are also useful for preparing suitable substantially linearinterpolymers, provided the proper catalysts and polymerizationconditions are employed. To polymerize the substantially linearinterpolymers useful in the invention, different catalysts can be used,but the polymerization process should be operated such that thesubstantially linear polymers are formed. That is, not allpolymerization conditions inherently make the substantially linearethylene polymers, even when the same catalysts are used.

For example, in one embodiment of a polymerization process useful inmaking the novel substantially linear ethylene interpolymers, acontinuous process is used, as opposed to a batch process.

Preferably, for substantially linear ethylene interpolymers, thepolymerization is performed in a continuous solution polymerizationprocess. Generally, manipulation of I₁₀/I₂ while holding M_(w)/M_(n)relatively low for producing the substantially linear ethylene polymersusing constrained geometry catalyst technology described herein is afunction of reactor temperature and/or ethylene concentration. Reducedethylene concentration and higher temperature generally produces higherI₁₀/I₂. Generally, as the ethylene concentration of the reactordecreases, the polymer concentration increases. For substantially linearethylene interpolymers, the polymer concentration for a continuoussolution polymerization process is preferably above about 5 weightpercent of the reactor contents, especially above about 6 weight percentof the reactor contents. Generally, the polymerization temperature ofthe continuous process, using constrained geometry catalyst technology,is from about 20° C. to about 180° C. If a narrow molecular weightdistribution polymer (M_(w)/M_(n) of from about 1.5 to about 2.5) havinga higher I₁₀/I₂ ratio (e.g. I₁₀/I₂ of about 7 or more, preferably atleast about 8, especially at least about 9) is desired, the ethyleneconcentration in the reactor is preferably not more than about 8 percentby weight of the reactor contents, especially not more than about 6percent by weight of the reactor contents, and most especially not morethan about 4 percent by weight of the reactor contents.

Multiple reactor polymerization processes can also be used in making theethylene interpolymers of the present invention, such as those processesdisclosed in copending applications Ser. No. 07/815,716, filed Dec. 30,1991 and Ser. No. 08/010,958, filed Jan. 29, 1993, and in U.S. Pat. No.3,914,342, the disclosures of all of which are incorporated herein byreference. The multiple reactors can be operated in series or inparallel or a combination thereof and/or with different Ziegler typecatalyst or single-site catalysts employed in the different reactors.

The term “block copolymer” is used herein to mean elastomers having atleast one block segment of an hard polymer unit and at least one blocksegment of an rubber monomer unit. However, the term is not intended toinclude thermoelastic ethylene interpolymers which are, in general,random polymers. Preferred block copolymers contain hard segments ofstyrenic type polymers in combination with saturated or unsaturatedrubber monomer segments. The structure of the block copolymers useful inthe present invention is not critical and can be of the linear or radialtype, either diblock or triblock, or any combination of thereof.Preferably, the predominant structure is that of triblocks and morepreferably that of linear triblocks.

The preparation of the block copolymers useful herein is not the subjectof the present invention. Methods for the preparation of such blockcopolymers are known in the art. Suitable catalysts for the preparationof useful block copolymers with unsaturated rubber monomer units includelithium based catalysts and especially lithium-alkyls. U.S. Pat. No.3,595,942 describes suitable methods for hydrogenation of blockcopolymers with unsaturated rubber monomer units to from blockcopolymers with saturated rubber monomer units. The structure of thepolymers is determined by their methods of polymerization. For example,linear polymers result by sequential introduction of the desired rubbermonomer into the reaction vessel when using such initiators aslithium-alkyls or dilithiostilbene and the like, or by coupling a twosegment block copolymer with a difunctional coupling agent. Branchedstructures, on the other hand, may be obtained by the use of suitablecoupling agents having a functionality with respect to the blockcopolymers with unsaturated rubber monomer units of three or more.Coupling may be effected with multifunctional coupling agents such asdihaloalkanes or alkenes and divinyl benzene as well as with certainpolar compounds such as silicon halides, siloxanes or esters ofmonohydric alcohols with carboxylic acids. The presence of any couplingresidues in the polymer may be ignored for an adequate description ofthe block copolymers forming a part of the composition of thisinvention.

Suitable block copolymers having unsaturated rubber monomer unitsincludes, but is not limited to, styrene-butadiene (SB),styrene-isoprene(SI), styrene-butadiene-styrene (SBS),styrene-isoprene-styrene (SIS),α-methylstyrene-butadiene-α-methylstyrene andα-methylstyrene-isoprene-α-methylstyrene, and the like.

The styrenic portion of the block copolymer is preferably a polymer orinterpolymer of styrene and its analogs and homologs includingα-methylstyrene and ring-substituted styrenes, particularlyring-methylated styrenes. The preferred styrenics are styrene andα-methylstyrene, and styrene is particularly preferred.

Block copolymers with unsaturated rubber monomer units may comprisehomopolymers of butadiene or isoprene and copolymers of one or both ofthese two dienes with a minor amount of styrenic monomer. When themonomer employed is butadiene, it is preferred that between about 35 andabout 55 mol percent of the condensed butadiene units in the butadienepolymer block have 1,2 configuration. Thus, when such a block ishydrogenated, the resulting product is, or resembles a regular copolymerblock of ethylene and 1-butene (EB). If the conjugated diene employed isisoprene, the resulting hydrogenated product is or resembles a regularcopolymer block of ethylene and propylene (EP). Preferred blockcopolymers with saturated rubber monomer units comprise at least onesegment of a styrenic unit and at least one segment of anethylene-butene or ethylene-propylene copolymer. Preferred examples ofsuch block copolymers with saturated rubber monomer units includestyrene/ethylene-butene copolymers, styrene/ethylene-propylenecopolymers, styrene/ethylene-butene/styrene (SEBS) copolymers,styrene/ethylene-propylene/styrene (SEPS) copolymers, and the like.

Hydrogenation of block copolymers with unsaturated rubber monomer unitsis preferably effected by use of a catalyst comprising the reactionproducts of an aluminum alkyl compound with nickel or cobaltcarboxylates or alkoxides under such conditions as to substantiallycompletely hydrogenate at least 80% of the aliphatic double bonds whilehydrogenating no more than about 25% of the styrenic aromatic doublebonds. Preferred block copolymers are those where at least 99% of thealiphatic double bonds are hydrogenated while less than 5% of thearomatic double bonds are hydrogenated.

The proportion of the styrenic blocks is generally between about 8 and65% by weight of the total weight of the block copolymer. Preferably,the block copolymers contain from 10 to 35 weight percent of styrenicblock segments and from 90 to 65 weight percent of rubber monomer blocksegments, based on the total weight of the block copolymer.

The average molecular weights of the individual blocks may vary withincertain limits. In most instances, the styrenic block segments will havenumber average molecular weights in the range of about 5,000 to about125,000, preferably from about 7,000 to about 60,000 while the rubbermonomer block segments will have average molecular weights in the rangeof about 10,000 to about 300,000, preferably from about 30,000 to about150,000. The total average molecular weight of the block copolymer istypically in the range of about 25,000 to about 250,000, preferably fromabout 35,000 to about 200,000. These molecular weights are mostaccurately determined by tritium counting methods or osmotic pressuremeasurements.

Further, the various block copolymers suitable for use in the presentinvention may be modified by graft incorporation of minor amounts offunctional groups, such as, for example, maleic anhydride by any of themethods well known in the art.

Block copolymers useful in the present invention are commerciallyavailable, such as, for example, supplied by Shell Chemical Companyunder the designation of KRATON and supplied by Dexco Polymers under thedesignation of VECTOR.

Generally, the novel thermoplastic elastomeric composition of thepresent invention comprises (a) from about 50 to about 99 percent byweight of the total composition of at least one block copolymer and (b)from about 1 to about 50 percent by weight of the total composition ofat least one ethylene interpolymer. Preferably, the novel compositioncomprises (a) from about 60 to about 95, and most preferably, from about70 to about 90 percent by weight of the total composition of at leastone block copolymer and (b) from about 5 to about 40, and mostpreferably, from about 10 to about 30 percent by weight of the totalcomposition of at least one ethylene interpolymer.

The novel thermoplastic elastomeric compositions of the presentinvention are further characterized as having:

(a) a storage modulus (E′) throughout the range of about −26° C. toabout 24° C. of less than about 3.5×10⁹ dynes/cm², more preferably lessthan 3×10⁹ dynes/cm²

(b) a ratio of storage modulus at −26° C. to storage modulus at 24° C.of less than about 4, preferably less than about 3, and

(c) storage moduli at −26° C. and 24° C. about 0.2 to about 3 times,preferably about 0.25 to about 2.6 times, more preferably about 0.4 toabout 2.2 times higher than the storage moduli at −26° C. and 24° C.,respectively, of the neat block copolymer portion of the composition.

Additives such as antioxidants (e.g., hindered phenolics (e.g., Irganox1010), phosphites (e.g., Irgafos 168)), cling additives (e.g.,polyisobutylene), antiblock additives, colorants, pigments, waxes,nucleating agents, extender oils, fillers, tackifers, and the like canalso be included in the present compositions, to the extent that they donot interfere with the substantial inertness or other enhancementsdiscovered by Applicants.

The compositions of the present invention are compounded by anyconvenient method, including dry blending the individual components andsubsequently melt mixing, either directly in the extruder used to makethe finished article, or by pre-melt mixing in a separate extruder ormixer such as, for example, a Haake unit or a Banbury mixer.

The novel compositions of the present invention can be fabricated intoarticles such as fibers, films, coatings and moldings by any of theknown methods in the art suitable for thermoplastic compositions. Thenovel compositions are particularly suitable for preparing fabricatedarticles from molding operations. Suitable molding operations forforming useful fabricated articles or parts from the novel compositions,including various injection molding processes (e.g., that described inModern Plastics Encyclopedia/89, Mid October 1988 Issue, Volume 65,Number 11, on pp. 264-268, “Introduction to Injection Molding” and onpp. 270-271, “Injection Molding Thermoplastics”, the disclosures ofwhich are incorporated herein by reference), blow molding processes(e.g., that described in Modern Plastics Encyclopedia/89, Mid October1988 Issue, Volume 65, Number 11, on pp. 217-218, “Extrusion-BlowMolding”, the disclosure of which is incorporated herein by reference)and profile extrusion.

Some of the fabricated articles include sporting goods such as wet suitsand golf grips, containers such as for food or other household articles,footwear counters, uppers and soles, automotive articles such as facia,trim and side molding, medical goods such as gloves, tubing, IV bags andartificial limbs, industrial goods such as gaskets and tool grips,personal care items such as elastic films and fibers for diapers,textiles such as nonwoven fabrics, electronic goods such as key pads andcable jacketing, and construction goods such as roofing materials andexpansion joint materials.

The present novel composition is also useful as a compounding ingredientor additive for such uses as asphalt modifications for crack repairingand roofing, polymer processing, impact and surface modifications,sealant and adhesive formulations, oil gel viscosity modifications andrubber extender/binder compounding.

The novel compositions of the present invention can also be furthercombined with other natural or synthetic resins to improve otherproperties. Suitable natural or synthetic resins include, but are notlimited to, rubbers, linear low density polyethylene (LLDPE), highdensity polyethylene (HDPE), low density polyethylene (LDPE),ethylene-vinyl acetate copolymer (EVA), ethylene-carboxylic acidcopolymers, ethylene acrylate copolymers, polybutylene (PB), nylons,polycarbonates, polyesters, polypropylene, ethylene-propyleneinterpolymers such as ethylene-propylene rubber, EPDM, chlorinatedpolyethylene, thermoplastic vulcanates, polyurethanes, as well asgraft-modified olefin polymers, and combinations thereof.

The invention will be further illustrated by means of the followingexamples without limiting the invention thereto.

EXAMPLES

In various evaluations the several different types of block copolymersand thermoelastic polymers are studied to determined their individualand combined properties. Property testing and determinations includeelastic and rheology as measured by dynamic mechanical and dynamicrheological techniques, Shore A hardness and processibility and processstability as measured by Haake torque technique. The description of thevarious block copolymers and thermoelastic polymers that are studied arelisted below.

Polymer Description Supplier VECTOR a styrene-butadiene-styrene blockcopolymer Dexco 8508 containing about 28% styrene by weight andPolymers. having a melt flow rate of about 12 VECTOR astyrene-isoprene-styrene block copolymer Dexco 4211 containing 30%styrene by weight and having Polymers a melt flow rate of about 13KRATON a styrene-ethylene-butene-styrene block Shell G1650 copolymerabout containing 29% styrene by Chemical weight and having a melt flowrate of less than Company about 0.1 ENGAGE a thermoelastic substantiallylinear The Dow EG8200 ethylene/1-octene copolymer prepared using aChemical constrained geometry catalyst system Company according toprocedures disclosed in U.S. Pat. No. 5,272,236 and 5,278,236 and havinga density of about 0.87 g/cc and a melt index, I₂, of about 5 g/10minutes TAFMER a thermoelastic homogeneously branched Mitsui P0480linear ethylene/propylene copolymer believed Chemical to be preparedusing a vanadium catalyst Company system and having a density of about0.87 g/cc and melt index, I₂, of about 1.0 g/10 minutes EXACT athermoelastic homogeneously branched Exxon 3027 linear ethylene/butenecopolymer believed to Chemical be prepared using a single-site catalystsystem Company and having a melt index, I₂, of about 3.2 g/10 minutesand a density of about 0.902 g/cc ATTANE a thermoelastic heterogeneouslybranched The Dow 4203 linear ethylene/1-octene interpolymer Chemicalprepared using a conventional Ziegler catalyst Company system and havinga density of about 0.905 g/cc and melt index, I₂, of about 0.8 g/10minutes EVA thermoelastic ethylene/vinyl acetate (EVA) — copolymercontaining about 18% by weight vinyl acetate and having a melt index,I₂, of about 3 g/10 minutes and a density of about 0.951 g/cc

Blend Composition Preparations

Blends of the various thermoelastic polymer with styrene blockcopolymers are prepared using a Haake mixer. Blends of thermoelasticpolymers with VECTOR 8508 and VECTOR 4211 are prepared at 170° C. for 7minutes at 60 rpm. The resins are dry blended before adding to Haakemixer. Antioxidant (Irganox B900) at 2000 ppm level is also added to theHaake mixing bowl. Blends of thermoelastic polymer with KRATON G1650 areprepared at 220° C. for 7 minutes at 60 rpm. A thin compression moldedplaque of partially fused KRATON G1650 is prepared at 200° C. using amelt press. Strips of the plaque is added to the molten thermoelasticpolymer already present in the mixing bowl.

Sample Preparation for Dynamic Mechanical and Rheological Measurements:

Samples for dynamic rheology studies are prepared in the form ofcircular disks using Haake torque blend compositions or from meltpressed pellets of the block copolymers as controls (i.e., no Haaketorque exposure). The samples are prepared at 190° C. and are air-cooledto ambient room temperature of about 23° C.

Samples for dynamic mechanical studies are prepared in the form of thinfilms (about 15-20 mil thick) from the Haake blend or from melt pressedpellets of the block copolymers as controls (i.e., no Haake torqueexposure). The samples are prepared at 190° C. and are cooled at 15°C./min to ambient room temperature of about 23° C.

Procedure for Dynamic Mechanical and Rheological Measurements:

The dynamic rheological properties of the samples are studied using aRheometrics RMS-800 rheometer. The frequency is varied from 0.1radians/second to 100 radian/second while the sample/unit temperature ismaintained at 190° C. in a nitrogen atmosphere. A strain of about 15% isalso used for the dynamic rheology measurement. In a few cases where theviscosity of resins or blend composition are high, the strain ismaintained at about 5%. According to the Cox-Mertz rule, the complexviscosity versus frequency data measured using the dynamic shearrheology is about equivalent to shear viscosity versus shear rate data,and as such, can provide useful information regarding the rheologicalproperties of the resins and resultant blend compositions.

The dynamic mechanical properties of the samples are studied usingRheometrics Solids analyzer RSA-II. The dynamic mechanical properties ofthe sample are measured at 5° C. increments in a nitrogen atmosphereover a temperature range of about −120° C. to highest possibletemperature at which sample either substantially melts or deforms. Theexperiments are conducted at a frequency of 10 radians/second and aninitial strain of 7.0×10⁻⁴. The sample dimensions are measured and areused in the calculations. The gauge length, that is the distance betweenthe clamps holding the sample during testing, is about 22 mm.

Examples 1-5

In a Haake mixing bowl, several thermoplastic blend compositions areprepared using ENGAGE EG8200 and VECTOR 8508. The blends consist ofVECTOR 8508 and ENGAGE EG8200 at weight percent ratios of 25/75, 50/50and 75/25, and are prepared at 170° C. and collected from the Haakemixing bowl after a total mixing time of about 6 to 7 minutes. Thesamples are compression molded for dynamic mechanical determinationsusing the procedure described above.

The dynamic mechanical results are shown in FIG. 1. The storage modulusdata at −26° C. and at 24° C., the −26° to 24° C. ratio and storagemodulus increase relative to neat VECTOR 8508 are shown in Table 1.

TABLE 1 Elasticity of Styrene/Butadiene/Styrene Blends Ratio of Ratio ofBlend to Blend to Neat Neat Storage Storage −26°/24° C. CopolymerCopolymer Ex- Modulus Modulus Storage Storage Storage am- (E′) at −26°C., (E′) at 24° C., Modulus Modulus at Modulus at ple Compositiondynes/cm² dynes/cm² Ratio −26° C. 24° C. 1  75% VECTOR 85O8 6.21 × 10⁸3.58 × 10⁸ 1.73 1.64 1.26  25% ENGAGE EG8200 2* 100% VECTOR 8508 3.79 ×10⁸ 2.83 × 10⁸ 1.34 — — 3  50% VECTOR 8508 3.50 × 10⁸ 1.19 × 10⁸ 2.940.92 0.42  50% ENGAGE EG8200 4*  25% VECTOR 8508 4.92 × 10⁸ 1.02 × 10⁸4.82 1.30 0.36  75% ENGAGE EG8200 5* 100% ENGAGE EG8200 5.77 × 10⁸ 8.92× 10⁷ 6.46 1.52 0.32 *Comparative example only; not an example of thepresent invention.

The dynamic mechanical data in FIG. 1 surprisingly reveals that additionof 25 and 50 weight percent ENGAGE EG8200 to VECTOR 8508 does notsubstantially alter the high temperature serviceability of the VECTOR8508 block copolymer. That is, the neat block copolymer (Example 2) andthe blend compositions comprising up to 50 weight percent ENGAGE EG8200(Examples 1 and 3) maintain good integrity as indicated by a stablestorage modulus at temperatures at least up to 50° C.).

FIG. 2 (which indicates the predicted dynamic mechanical response of thecompositions based on weight average contributions of the componentmaterials) and Table 1 show that the ratio of storage modulus at −26° C.to storage modulus at 24° C. does not increase as rapidly as expectedbased on weight average contribution of the two components. In factthese blend compositions are, surprisingly, more elastic than predicted,especially at a concentration of about 25 weight percent ENGAGE EG8200.

Table 1 also indicates that the storage modulus measured at −26° C. and24° C. for the 25 weight percent ENGAGE EG8200 blend composition(Example 1) does not change significantly relative to neat blockcopolymer VECTOR 8508 at the same temperatures. The storage modulus at−26° C. and 24° C. for Examples 1 and 3 are only about 0.42 to about1.64 times higher than the storage modulus at −26° C. and 24° C. of neatVECTOR 8508. Such storage modulus differences are consideredinsignificant and, thereby, exemplify effective use of ENGAGE EG8200 asan extender for VECTOR 8508.

A low −26° to 24° C. storage modulus ratio (i.e., less than about 4) incombination with stable, low storage moduli (i.e., less than about3.5×10⁹ dynes/cm²) over the same temperature range indicates that thecomposition possesses good elasticity in the range of at least about−26° C. to about 24° C. This attribute is important for products thatmust maintain their shape, integrity and performance over the selectedtemperature range.

Similar to the dynamic mechanical storage modulus results, FIG. 3indicates the addition of amounts less than about 50 weight percent ofENGAGE EG8200 does not substantially alter the dynamic rheologicalproperties of VECTOR 8508, i.e., the response is characteristic of theblock copolymer and not that of the ethylene interpolymer. FIG. 3indicates at low shear rates there is essentially no change in dynamicviscosity relative to the neat block copolymer and at high shears rates,there is only a slight decrease in viscosity, particularly when 25weight percent of ENGAGE EG8200 is admixed with the block copolymer.

By not substantially altering the high temperature serviceability anddynamic mechanical and rheological properties of VECTOR 8508, theseresults indicate that ENGAGE EG8200 functions as substantially inertextender in blend combinations with the block copolymers.

Examples 6-10

Blends consisting of VECTOR 4211 and ENGAGE EG8200 at weight ratios25/75, 50/50 and 75/25 are prepared in the same manner as describedabove for Examples 1-5. The samples are prepared for dynamic mechanicaland rheological determinations using the procedure described above. Theresults are shown in FIGS. 4, 5 and 6. The storage modulus data at −26°C. and at 24° C. and the temperature to temperature storage modulusratio as well as the blend composition to neat block copolymer storagemodulus ratio are all shown in Table 2.

TABLE 2 Elasticity of Styrene/Isoprene/Styrene Blends Ratio of Ratio ofBlend to Blend to Neat Neat Storage Storage −26°/24° C. CopolymerCopolymer Ex- Modulus Modulus Storage Storage Storage am- (E′) at −26°C., (E′) at 24° C., Modulus Modulus at Modulus at ple Compositiondynes/cm² dynes/cm² Ratio −26° C. 24° C. 6  75% VECTOR 4211 2.26 × 10⁸8.99 × 10⁷ 2.51 2.13 1.95  25% ENGAGE EG8200 7* 100% VECTOR 4211 1.06 ×10⁸ 4.60 × 10⁷ 2.30 — — 8  50% VECTOR 4211 2.96 × 10⁸ 8.55 × 10⁷ 3.462.79 1.86  50% ENGAGE EG8200 9*  25% VECTOR 4211 4.71 × 10⁸ 9.51 × 10⁷4.95 4.44 2.07  75% ENGAGE EG8200 10* 100% ENGAGE EG8200 5.77 × 10⁸ 8.92× 10⁷ 6.46 5.44 1.94 *Comparative example only; not an example of thepresent invention.

FIG. 4 surprisingly reveals that addition of 25% and 50% ENGAGE EG8200to VECTOR 4211 did not substantially alter the high temperatureserviceability of the block copolymer. Table 2 and FIG. 5 show that theratio of storage modulus at −26° C. to storage modulus at 24° C. forthese samples do not substantially increase as predicted based on theweight percentage contributions of the two components. Similar to theabove Examples 1 and 3, ENGAGE EG8200/VECTOR 4211 blends comprising upto 50 weight percent ENGAGE EG8200 (Examples 6 and 8) are surprisinglymore elastic than expected.

Also, the −24° to 24° C. storage modulus ratio of Examples 6 and 8 areless than 4 and their storage moduli at −26° C. and 24° C., which rangefrom 1.86 to 2.79 times higher, are not substantially different fromthat of neat VECTOR 4211. Similar to the dynamic mechanical storagemodulus results, FIG. 6 indicates the addition of amounts up to about 50weight percent of ENGAGE EG8200 does not substantially alter the dynamicrheological properties of VECTOR 4211, particularly when 25 weightpercent of ENGAGE EG8200 is admixed with the block copolymer. Theseelasticity and rheological results indicate that ENGAGE EG8200 functionsas essentially as a substantially inert extender in blend combinationswith VECTOR 4211, a styrene/isoprene/styrene block copolymer.

Examples 11-15

In another evaluation using the same sample preparation and testingprocedures indicated in Examples 1-5 above, similar results are obtainedfor blend compositions comprising KRATON G-1650 and ENGAGE EG8200. FIGS.7 and 8 and Table 3 show that for blend compositions comprising lessthan 50 weight percent ENGAGE EG8200, the dynamic properties of suchblends are substantially unchanged relative to neat KRATON G-1650.

TABLE 3 Elasticity of Styrene/Ethylene-Butene/Styrene Blends Ratio ofRatio of Blend to Blend to Neat Neat Storage Storage −26°/24° C.Copolymer Copolymer Ex- Modulus Modulus Storage Storage Storage am- (E′)at −26° C., (E′) at 24° C., Modulus Modulus at Modulus at pleComposition dynes/cm² dynes/cm² Ratio −26° C. 24° C. 11  75% KRATONG1650 9.13 × 10⁸ 2.71 × 10⁸ 3.37 0.44 0.25  25% ENGAGE EG8200 12* 100%KRATON G1650 2.08 × 10⁹ 1.06 × 10⁹ 1.96 — — 13  50% KRATON G1650 5.89 ×10⁸ 1.31 × 10⁸ 4.50 0.28 0.12  50% ENGAGE EG8200 14*  25% KRATON G16506.34 × 10⁸ 1.27 × 10⁸ 4.99 0.30 0.12  75% ENGAGE EG8200 15* 100% ENGAGEEG8200 5.77 × 10⁸ 8.92 × 10⁷ 6.46 0.28 0.08 *Comparative example only;not an example of the present invention.

Examples 6, 7, 17-20

In another evaluation, the above Haake torque sample preparation anddynamic mechanical testing procedures are performed using 25 weightpercent of several different thermoelastic polymers in a VECTOR 4211block copolymer. The thermoelastic polymers include ENGAGE EG8200,ATTANE 4203, TAFMER P0480, EXACT 3027 and an 18 weight percent vinylacetate EVA copolymer. Table 4 shows the description of the blendcompositions and their respective storage modulus data. FIG. 9 shows thestorage modulus versus temperature data for the blend compositions. FIG.9 and Table 4 indicate all the thermoelastic polymers in the evaluationfunction as a substantially inert extender for VECTOR 4211, except theEVA copolymer. While the −26° to 24° C. storage modulus ratio of the EVAblend composition (Example 19) is low and similar to the otherthermoelastic blend compositions in the evaluation, the storage modulusof the EVA blend composition at −26° C. and 24° C. is several timeshigher (i.e., 4.3 and 5.92 times higher) than that for the correspondingneat block copolymer (Example 7).

TABLE 4 Blend Composition Descriptions For Various ThermoelasticPolymers at 25 Weight Percent Ratio of Ratio of Blend to Blend to NeatNeat Storage Storage −26°/24° C. Copolymer Copolymer Ex- Modulus ModulusStorage Storage Storage am- (E′) at −26° C., (E′) at 24° C., ModulusModulus at Modulus at ple Composition dynes/cm² dynes/cm² Ratio −26° C.24° C. 6  75% VECTOR 4211 2.26 × 10⁸ 8.99 × 10⁷ 2.51 2.13 1.95  25%ENGAGE EG8200 7* 100% VECTOR 4211 1.06 × 10⁸ 4.60 × 10⁷ 2.30 — — 17  75%VECTOR 4211 2.02 × 10⁸ 8.59 × 10⁷ 2.35 1.91 1.87  25% ATTANE 4203 18 75% VECTOR 4211 1.87 × 10⁸ 8.12 × 10⁷ 2.30 1.76 1.77  25% TAFMER P048019*  75% VECTOR 4211 6.27 × 10⁸ 1.98 × 10⁸ 3.17 5.92 4.30  25% EVA(18%VA)  75% VECTOR 4211 20  25% EXACT 3027 2.20 × 10⁸ 9.33 × 10⁷ 2.36 2.072.03 *Comparative example only; not an example of the present invention.

Examples 1, 2, 20 and 21

Table 5 below indicates that although ATTANE 4403 does not appear tosubstantially alter the storage modulus/elasticity of block copolymers,it does substantially alter the hardness of the VECTOR 8508 blockcopolymer at 25 weight percent addition levels and, as such, like EVAcopolymers, is not a substantially inert thermoelastic extender withinthe purview of the present invention. Changes in Shore A hardnessgreater than about ±3 units (as measured by ASTM-D2240) is considered tobe a substantial alteration. The inability of ATTANE 4203 to perform asan inert extender is believed to be due to its higher polymer density(i.e., 0.905 g/cc). Similarly, at least for compositions consistingessentially of block copolymers with unsaturated rubber monomersegments, as the density of the ethylene interpolymer used in thepresent invention decreases, proportionally higher amounts of theethylene interpolymer are permissible while still maintaining thesubstantial inertness discovered by the Applicants. See Examples 3 and8.

TABLE 5 Effect of Thermoelastic Polymers on Block Copolymer HardnessShore A Example Composition Hardness  1  75% VECTOR 8508 73  25% ENGAGEEG8200  2* 100% VECTOR 8508 74 20  75% VECTOR 8508 73  25% TAFMER P048021*  75% VECTOR 8508 78  25% ATTANE 4203 *Comparative example only; notan example of the present invention.

Example of Melt Fusion for Block Copolymer with Saturated Rubber Units

In still another evaluation the response of KRATON G1650 to thermalprocessing is determined in a Haake torque mixer. As shown in FIGS. 10and 11, Haake torque evaluation results indicate that ENGAGE EG8200functions as a fusion promoter and substantially improves theprocessability of KRATON G1650. FIG. 10 shows the Haake torque of neatKRATON G1650 at 240° C. At 230° C., neat KRATON G1650 (Example 12 blockcopolymer) does not melt in a Haake torque mixer. At 240° C., aninduction delay time of about 3 minutes is required to melt and fuseKRATON G1650 into a molten processable sample. In addition to theincrease energy requirement, FIG. 10 indicates an additional processingdisadvantage. As a consequence of the delay time, FIG. 10 indicates theneat block copolymer is rendered more susceptible to thermal scission(instability) as manifested by significant torque decreases over thetest period.

However, FIG. 11 indicates the addition of 25 weight percent of ENGAGEEG8200 (Example 11 blend composition) allows melting and fusion afterabout 1 minute of processing at a lower processing temperature, i.e.,below 220° C. FIG. 11 also indicates the resultant blend composition ismore thermally stable as indicated by a moderate torque increase over anextended test period. FIG. 12, where the blend composition comprises 50weight percent TAFMER P0480 in KRATON G1650 (Example 22), indicatessimilar results regarding fusion and processibility enhancement areobtainable using TAFMER P0480.

Example for Thermal Processing Improvement for Block Copolymer withUnsaturated Rubber Units

In still another evaluation, the dynamic mechanical properties of VECTOR4211 is repetitively determined with and without exposure to a Haaketorque mixer as described in the blend composition sample preparationprocedures above. Table 6 shows the sample descriptions for thisevaluation and FIG. 13 shows the storage modulus elasticity data. Acomparison between Examples 7 and 23 on the one hand and Examples 24-26as plotted in FIG. 13 indicates VECTOR 4211 is highly sensitive to Haaketorque exposure. Further, a comparison between Examples 24-26 as plottedin FIG. 13 and Examples 6, 17, 18 and 20 as plotted in FIG. 9 showsvarious thermoelastic polymers(i.e., ATTANE 4203, TAFMER P0480, EXACT3027 and ENGAGE EG8200 at 25 weight percent loadings) can significantlyimprove the Haake thermal shear or processing stability of the KRATONG1650 block copolymer. That is, these polymers allow lower storagemoduli throughout the temperature range of −26° C. to 24° C. that betterapproximates the neat, non-Haake exposed block copolymer (Examples 7 and23) while the neat block copolymer shows higher storage modulithroughout the same range when processed in the Haake mixer (Examples24-26). However, a comparison between EVA blend compositions at 25 and50 weight percent in VECTOR 4211 as plotted in FIG. 9 with the neat,Haake expose block copolymers (Examples 24-26) as plotted in FIG. 12indicates EVA does not provide similar improvements in thermalstability.

TABLE 6 Haake Exposure of VECTOR 4211 Haake Exposure Example 7 min. at60 rpm  7* 100% None VECTOR 4211 23* 100% None VECTOR 4211 24* 100% YesVECTOR 4211 25* 100% Yes VECTOR 4211 26* 100% Yes VECTOR 4211*Comparative example only; not an example of the present invention.

We claim:
 1. A thermoplastic elastomeric composition comprising fromabout 70 to about 90 percent by weight, based on the total weight of thecomposition, of an unsaturated styrene triblock copolymer containingabout 10 to 35 weight percent styrene and from about 10 to about 30percent by weight, based on the total weight of the composition, of ahomogeneously branched linear ethylene interpolymer characterized as aninterpolymer of ethylene with at least one C₃-C₂₀ α-olefin and as havinga density from about 0.855 to about 0.905 g/cc and a short chainbranching distribution index (SCBDI) of greater than 50 percent, whereinthe homogeneously branched linear ethylene interpolymer in the amountemployed is a substantially inert extender of the triblock copolymer andwherein the composition is further characterized as having: i. storagemoduli throughout the range of −26° C. to 24° C. of less than about3.5×10⁹ dynes/cm², ii. a ratio of storage modulus at −26° C. to storagemodulus at 24° C. of less than about 3, and iii. storage moduli at −26°C. and 24° C. about 0.4 to about 2.2 times higher than the storagemoduli at −26° C. and 24° C., respectively, of the neat styrene blockcopolymer portion of the composition.
 2. The composition of claim 1wherein the unsaturated styrene triblock copolymer is selected from thegroup consisting of styrene/butadiene/styrene, styrene/isoprene/styrene,α-methylstyrene/butadiene/α-methylstyrene, andα-methyl-styrene/isoprene/α-methylstyrene block copolymers.
 3. Thecomposition of claim 1 wherein the unsaturated styrene triblockcopolymer is a styrene/butadiene/styrene block copolymer.
 4. Thecomposition of claim 1 wherein the unsaturated styrene triblockcopolymer is a styrene/isoprene/styrene block copolymer.
 5. Thecomposition of claim 1 wherein the at least one C₃-C₂₀ α-olefin isselected from the group consisting of propylene, isobutylene, 1-butene,1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, and1-decene.
 6. The composition of claim 1 wherein the homogeneouslybranched linear ethylene interpolymer is a copolymer of ethylene and aC₃-C₂₀ α-olefin.
 7. The composition of claim 5 wherein the homogeneouslybranched linear ethylene interpolymer is a homogeneously branched linearethylene/1-butene copolymer.
 8. The composition of claim 5 wherein thehomogeneously branched linear ethylene interpolymer is a homogeneouslybranched linear ethylene/1-hexene copolymer.
 9. The composition of claim5 wherein the homogeneously branched linear ethylene interpolymer is ahomogeneously branched linear ethylene/1-octene copolymer.
 10. Thecomposition of claim 1 wherein the homogeneously branched ethyleneinterpolymer is further characterized as lacking a high density polymerfraction in that the interpolymer does not contain a polymer fractionwith a degree of branching less than or equal to 2 methyls/1000 carbons.11. A fabricated article in the form of a film, fibers or a moldedarticle comprising from about 70 to about 90 percent by weight, based onthe total weight of the composition, of an unsaturated styrene triblockcopolymer containing about 10 to 35 weight percent styrene and fromabout 10 to about 30 percent by weight, based on the total weight of thecomposition, of a homogeneously branched linear ethylene interpolymercharacterized as an interpolymer of ethylene with at least one C₃-C₂₀α-olefin and as having a density from about 0.855 to about 0.905 g/ccand a short chain branching distribution index (SCBDI) of greater than50 percent, wherein the homogeneously branched linear ethyleneinterpolymer in the amount employed is a substantially inert extender ofthe triblock copolymer and wherein the composition is furthercharacterized as having: i. storage moduli throughout the range of −26°C. to 24° C. of less than about 3.5×10⁹ dynes/cm², ii. a ratio ofstorage modulus at −26° C. to storage modulus at 24° C. of less thanabout 3, and iii. storage moduli at −26° C. and 24° C. about 0.4 toabout 2.2 times higher than the storage moduli at −26° C. and 24° C.,respectively, of the neat styrene block copolymer portion of thecomposition.
 12. The composition of claim 1 wherein the ethyleneinterpolymer has a density in the range of about 0.86 g/cc to about 0.89g/cc.
 13. The composition of claim 10 wherein 25 percent by weight ofthe total composition is the unsaturated styrene triblock copolymer.